Process of recovering sulfuric anhydrid and sulfuric-acid vapors from gases.



PATENIED MAY 9, i905. M. SCHROBDBR. ,'PRocEss or RBCOVERING SULPURIGANHYDRID AND SUL-Fumo ACID VAPQRS FROM GASES. APPLIUATION 11.31) JULY17, 190s.

Xo. 789,63t

Patented Hay 9, 1905.

UNITED STATES PATENT OFFICE.

MAX SCHROEDER, OF BERLIN, GERMANY, ASSIGOR TO NEW JERSEY .ZINC COMPANY,OF `NEW YORK, N. Y., A CORPORATION OF NE'W JERSEY,

PROCESS F RECOVEiilNG'SULFURlC ANHYDRlD AND SULFURlC-AClD VAPORS FROMGASES.

SPECIFICATION forming part of i Letters Patent No. 789,634, dated May 9,1 905.

Application led July 17, 1G03. Beriai Nc. 165,960. y

To (LZ1 whom. may concern:

Be it known that I. MAxSonnoEDen, asuh- .ject of the German Emperor,residing at Klopstockstrasse 45, Berlin, N. W., E23, Germany, 5 haveinvented certain new and useful Improvements in Processesof RecoveringSulfu ric An- Ahydrid and Suifuric-Aeid Vapors from Gases v .Goiinimr'lhem; and 1 do hereby deciare the follmlmg to be a full, clear,and exact description of the invention, such as will enable othersskilled in the art to which it appertains to make and use the same.

Thecondcnsationofsulfnricanhydrid(made by the Contact or catalyticprocess or otherwise) is etl'ecte'i by absorption in .sulfuric acid. Themore concentrated the acid the higher its capacity for absorption. IfSO; gases are passed through or over ninety-nine per cent. sulfuricacid, the SO; is rapidly and completelyY absorbed. AiVith ninety-tirepercent. acid comparatively `little mist is produced. If the strength ofthe absorption acid is below ninety per cent., a considerable quantityof mist is formed, and still more if weaker acid is ust-d.Thisphenomenonisattribuiable to the fact that weak sulfuric acid givesup water-vapor to the gas, which combines with a part of the transparentSOL, making H.S(), which is visible in the gas as a fog or mist. 39 Whenthis fog or mist of sulfuric acid is once formed, it is almostimpossible to condense it by the means heretofore employed for thepurpose. The mist or fog passes through absorption acid of ninety-tiveto ninety-nine per cent. almost unchanged, whereas this strong acidcatches S05 almost com plete-ly. The styles of apparatus heretoforeemployed, whether the. gas is passed over the surface of the liquid oris forced through i or passed 40 through a spray of the liquid, haveshown themselves to be almost inoperative as retainers of thesesulfuric-acid mists. For this `.-.,reason the lite-,dure of the art iscareful to f. point out that the sulfuric anhydrid should be absorbed byacid of at least ninety-seven `per cent., and not by sulfuric acid of amateriallylower degree of concentration. In

many cases it is desirable to effect the absorption of the anhydrid bymore dilute acids.

For instance, this is the case when the absorption-acid is obtainedfromthe operation of lead chamliers. Because the acid so obtained is neverstronger than 60;' Baum (77.6 per cent.) it has heretofore beenconsidered necessary to mix it with highly-concentrated or fuming acidenough to give the mixture a strength of about ninety-tive per cent. orto restrict the quantity added to the acid -in the absorbers to anamount that would not lower the strength of the mixture much below thispoint. This consumes time, and constant supervision is required toinsure the proper maintenance of the grade. lt is simpler to allow theweak absorption acid totiow directly into the lirst of a series ofabsorbing vessels, in which its grade is gradually raised by theabsorption of SO:n By dividing the absorption among several vessels inthis way the evolution of beat is not so great at any point as torequire artiticiai cooling. This method of '.vorking, however. has notbeen practicable, owing to the extreme difiiculty of condensing the sulfurie-acid mists which are formed when sulfuric-anhydrid gases arebrought in contact with comparatively dilute sulfurcacid. The presentinvention provides a simple method for completely1 and speedilycondensing these sulfurie-acid mists. This method consists in passingthe gases through line-grained or linetibered acidfproof materiaLs-uchaseoarsesand, broken stone, glass-wool, or the like. ln order todiminish the resistance to the passage of the gas as far as possible,the line material should `be spread out in wide layers of moderateheight. The large area obtained in this 35 way reduces t'he friction tosuch a degree that it is practically not worth considering, even if alayer of from one to one and a half meters should be employed. Thereceptacles for the layers of granular or fibrous material may 9o betight boxes or tanks,of iron or other suitable material, withappropriate gas-inlet and gas-outlet nipples and with a cock for drawingott' the condensed acid. The line material employed is .placed upon agrate or perforateo plate within the/receptacle, upon which ire;eptacle.which should be suitably lined with acid-proof material. andIl' indicate the gasconduits, either of which may serve for the in' lctof the gaseous mixture containing the SO gases, according as the flowthrough the material is frombelow-upward or from aboi'e downward. 'lhegrate or bottom (I supports the initial lay er of coarser material c,which iu its turn supports the layer of tiner material j'. A pipe u,terminating in a longitudinal sprinkliIig-head,distributes theabsorption acid upon this materiai, as herein described. 'lhe cock fordrawing otf the condensed acid is indicated by c. l1' we select as thematerial 7" coarse-grained sand of a diameter of one to threemillimeters, one cubic meter of sand is suliicient to almost completelyYfree about one hundred meters of the gas per hour from sulfuric-acidmists. fe may also use coax-ser material up to about one -half-inch sizeof grain; but by so doing we lose in the intensity of the operation. Onthe other hand, the grains must not be too small, because sand that istoo tine oers too great a resistance to the passage of the gases andwhen wet with the absorbing acid would form an impenetrable mass. lt iaalso desirable to provide the receptacle with a sprinkling de'- vice, asshown.l so that the material can be sprinkled with sulfuric acid in casethe gases have not taken up sullicent water to convert all of the anhydrid to sulfuric-acid mist in the preliminary absorption plant. This freeanhyd rid might escape absorption unless dilute sulfuric acid waspresent at this point to combine with and retain it.

Having thus described my invention, what Iclaim is-- 1. The process ofseparating sulfuric-acid mists or fogs from gases containing them, whichconsists in conducting the gases containing the said mists or fogsthrough a body of finely-divided material; substantially as described.

2. The process of separating sulfuric-acid mists or fogs from gasescontaining them and simultaneously recovering and absorbing any freesulfuric anhydrid present in such gases, which consists in conductingthe gases containing them through a body of finely-divided material andsaturating said material with sulfuric'acid; substantially as described.

1n testimony whereof I afiix my signature in presence of two witnesses.

MAX 'SCHROEDER "Vitnesses:

HENRY HAsPER, WOLDEMAR HAUPT.

